首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   28902篇
  免费   2427篇
  国内免费   689篇
耳鼻咽喉   140篇
儿科学   496篇
妇产科学   412篇
基础医学   3942篇
口腔科学   423篇
临床医学   2042篇
内科学   3920篇
皮肤病学   199篇
神经病学   1912篇
特种医学   1248篇
外国民族医学   2篇
外科学   1093篇
综合类   3312篇
现状与发展   3篇
预防医学   2173篇
眼科学   706篇
药学   6243篇
  16篇
中国医学   2092篇
肿瘤学   1644篇
  2024年   101篇
  2023年   532篇
  2022年   810篇
  2021年   1441篇
  2020年   1112篇
  2019年   971篇
  2018年   921篇
  2017年   968篇
  2016年   1017篇
  2015年   1071篇
  2014年   1604篇
  2013年   2131篇
  2012年   1578篇
  2011年   1592篇
  2010年   1296篇
  2009年   1249篇
  2008年   1279篇
  2007年   1258篇
  2006年   1016篇
  2005年   955篇
  2004年   842篇
  2003年   800篇
  2002年   661篇
  2001年   573篇
  2000年   525篇
  1999年   496篇
  1998年   365篇
  1997年   329篇
  1996年   309篇
  1995年   332篇
  1994年   317篇
  1993年   273篇
  1992年   267篇
  1991年   288篇
  1990年   275篇
  1989年   208篇
  1988年   199篇
  1987年   169篇
  1986年   150篇
  1985年   204篇
  1984年   210篇
  1983年   135篇
  1982年   147篇
  1981年   125篇
  1980年   132篇
  1979年   93篇
  1978年   79篇
  1977年   57篇
  1976年   72篇
  1975年   49篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
51.
The conversion of multiple whole blood donors to apheresis donors is a challenge since a rapidly expanding apheresis donor base could erode homologous collections. We addressed this concern with a plan to enhance apheresis recruitment as well as donations among homologous donors with types O and B blood. Focusing the donor's attention on blood type as it relates to type-specific product needs was the basis of our approach. A matrix was used to recruit the desired types for the desired procedures (whole blood, platelet/plasma apheresis). The matrix instructed donors of blood types O, A-, and B- to primarily give whole blood and to give apheresis as a secondary donation. Donors AB, A+, and B+ were primarily directed to apheresis donations, whole blood donation being secondary. A+ and O- donors only gave their secondary donation if they were at maximum donations with the primary donation. The collections by blood type in percentages for 12 months of 1992/93 for whole blood were O+ 38.9, 0- 7.3, A+ 29.5, A- 5.7, B+ 11.9, B- 2.1, AB+ 3.7, AB+ 0.7. For apheresis it was 0+ 36.2, 0- 6.7, A+ 33.0, A- 6.6, B+ 10.4, B- 1.2, AB+ 4.9, AB+ 1.0. In 1992/93, A+ and B+ apheresis collections as compared to total apheresis collections increased by 4.9% and 13.7%, respectively. For O group apheresis donations, a decrease of 2.5% was shown and A+ whole blood donations decreased by 5.35%. During the same period of time, total apheresis collections increased by 3,058 units. We demonstrated that integration of apheresis recruitment with type-specific whole blood recruitment yielded significant increases of type-specific products.  相似文献   
52.
1. The authors investigated the effect of two extrahepatic cholestasis models (one by bile duct ligation and the other by choledocho-jugular fistula) on the hepatic clearance of horseradish peroxidase in male Sprague-Dawley rats divided into four groups. 2. In groups A (n = 5 rats) and B (n = 5), bile duct ligation was performed, while a choledocho-jugular fistula was created in groups C (n = 5) and D (n= 7). A 10 mg intravenous bolus of horseradish peroxidase was injected after 24 h (groups A and C), 48 h (groups B and D) or 1 h (Group E; five sham-operated rats). Serum and bile samples were then serially collected for 2 h. 3. In all groups, serum horseradish peroxidase levels increased soon after injection and then rapidly decreased, the curves being similar. Biliary excretion increased for 30 min and then slowly decreased. The highest horseradish peroxidase biliary concentrations and outputs were found in Group B followed by Group A; both groups had significantly higher levels than Group E. No difference was found between horseradish peroxidase biliary excretion of groups C and D and that of sham-operated rats. 4. When each group was considered separately, sampling times correlated with the corresponding ratios of bile/ plasma HRP. Significant differences were found between the relative slopes of groups A, B and E, but not between those of groups C, D and E. 5. In conclusion, bile duct obstruction greatly affects the plasma-bile transfer of fluid phase markers, such as horseradish peroxidase, while single retention, caused by choledocho-jugular fistula, has no influence. The increased biliary hyperpressure related to the duration of cholestasis may account for the degree of horseradish peroxidase transfer which, in turn, probably depends on an enhanced paracellular passage.  相似文献   
53.
用刀豆蛋白A刺激激素敏感型肾病单个核细胞,并将其培养上清液灌注于大鼠肾内。结合电镜观察,用图像分析仪及体视学方法分别对其肾组织胶体铁染色切片和电镜照片上的足突和滤过裂隙的平均宽度进行测定。结果表明:该病极期上清液灌注的鼠肾小球多阴离子明显减少,足突肿胀、融合,滤过裂隙变窄;而该病缓解组和正常对照组则为阴性。说明该病单个核细胞培养上清液可引起鼠肾小球微小病变型肾病综合征的病变,并揭示该变化可能是由其上清液中一种异常的T淋巴细胞因子所致。  相似文献   
54.
55.
The kinetics of a single i. v. dose of theophylline given either alone or with flumequine was studied in eight healthy volunteers. No statistically significant differences were observed in the pharmacokinetic parameters of theophylline (volume of distribution, elimination half-life, AUC, plasma clearance) following the two treatments.Pretreatment for 5 days with oral flumequine (400 mg, three times daily) had no significant effect on the disposition of a single i. v. dose of theophylline in healthy volunteers.  相似文献   
56.
宝鸡市城市饮用水与人群健康效应的调查研究   总被引:1,自引:1,他引:0  
本文通过对宝鸡市居民饮自来水和自备井水的人群进行了回顾性和前瞻性调查分析,结果发现,饮自来水与饮未经处理自备井水明显的差异。即调查组(饮自来水)肠道传染病发病率为4.22%和6.82%,对照组(饮自备井水)发病率为7.71%和11.56%经卡方检验P<0.05,差异有显著性。从发病病种来看,调查组和对照组均以腹泻为主,其次为痢疾和肝炎,发病率分别是:腹泻,调查组为35.59‰和63.00‰,对照组  相似文献   
57.
Hep-2, human epithelial carcinoma cells, and human foreskin fibroblasts (FF9 and FF13) were exposed to either an ultrafiltrate (< 50 kD) of human sera or the weak base, procaine hydrochloride, to induce reversible cytoplasmic vacuolization. The formation of vacuoles was shown not to be due to imbibition of medium. Ultrastructural details obtained from various stages of vacuole formation were compared. In both cases of induction vacuoles were irregular and often appeared membraneless, with little in the way of electron-dense content. They started to form in the perinuclear cytoplasm and progressed towards the periphery. Osmotic stress was not involved since mitochondria remained normal throughout a vacuolization episode.
Vacuoles were often seen in close contact with filamentous structures, and this association remained detectable at late stages of the phenomenon. Fluorescent visualization of F-actin confirmed that the vacuoles were frequently bordered by microfilaments. No major metabolic impairment was apparent in vacuolized cells as judged by protein synthesis measurements, but nuclear fluorescence (DNA content) and forward light scatter (nuclear volume) by flow cytometric analysis suggested late S phase and G2 retardation. 1H-nmr relaxation measurements indicated intracellular water restricted in motional characteristics in vacuolized cells. The possibility of a restricted cytoplasmic phase separation as part of a transient adaptation response is raised, and a hypothesis to explain the findings is discussed.  相似文献   
58.
Abstract We tried melatonin treatment in two patients with non-24 h sleep-wake syndrome, who did not respond to treatments by vitamin B12, bright light therapy, or hypnotics. In one patient, melatonin 5–10 mg improved difficulty in falling asleep and in waking, although it failed to improve the sleep-wake rhythm. In another patient, melatonin 3 mg successfully changed the sleep-wake rhythm from free-running pattern to delayed sleep phase pattern. However, melatonin re-administration after a 4-month drug-free interval failed to improve his free-running sleep-wake rhythm. These results suggest that melatonin acted as a sleep inducer in one patient and as a phase setter in the other, although the effect on the latter patient was transient.  相似文献   
59.
公共关系与新闻传播紧密相连 ,有什么样的新闻传播 ,就有什么样的公共关系。公共关系的活动过程 ,主要就是一个组织与公众之间进行信息传播和沟通的过程。能否有效地利用各种新闻传播媒介 ,造就有利的舆论环境 ,是能否成功地组织开展各类公共关系活动的关键  相似文献   
60.
Abstract It is a fundamental assumption in nursing theory that it is important for nurses to understand how patients think about themselves and the contexts they are in. According to modern theories of hermeneutics, a nurse and a patient must share the same concepts in order to communicate beliefs with the same content. But nurses and patients seldom understand medical concepts in exactly the same way, so how can this communicative aim be achieved in interaction involving medical concepts? The article uses a theory of concepts from recent cognitive science and philosophy of mind to argue that nurses and patients can share medical concepts despite the diversity of understanding. According to this theory, two persons who understand medical language in different ways will nevertheless possess the same medical concepts if they agree about the normative standards for the applications of the concepts. This entails that nurses and patients normally share medical concepts even though patients’ conceptions of disease and illness are formed in idiosyncratic ways by their social and cultural contexts. Several practical implications of this argument are discussed and linked to case studies. One especially important point is that nurses should seek to make patients feel comfortable with deferring to a medical understanding. In many cases, an adequate understanding of patients presupposes that nurses manage to do this. Another implication is that deference‐willingness to normative meaning is not equivalent to the actual application of concepts. Deference‐willingness should rather be thought of as a pre‐communicative attitude that it is possible for patients who are not fully able to communicate to possess. What is important is that nurses and patients have the intention of conforming to the same meaning.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号